Piezoelectric/electrostrictive actuators have the advantage of being capable of precisely controlling displacement in the order of submicrons. In particular, piezoelectric/electrostrictive actuators using the sintered body of a piezoelectric/electrostrictive ceramic composition as the piezoelectric/electrostrictive body further have the advantages of offering high electric-mechanical conversion efficiency, high generation power, high response speed, high durability, and low power consumption, in addition to the advantage of being capable of precisely controlling displacement. For these advantages, such piezoelectric/electrostrictive actuators have been adopted for the heads of inkjet printers and the injectors of diesel engines.
As the piezoelectric/electrostrictive ceramic compositions for piezoelectric/electrostrictive actuators, Pb (Zr, Ti)O3(PZT)-based piezoelectric/electrostrictive ceramic compositions have been conventionally used, but (Li, Na, K)(Nb, Ta)O3-based piezoelectric/electrostrictive ceramic compositions are also studied since concerns are rising that the elution of lead from sintered bodies seriously influences the global environment.
Also, as described in Japanese Patent Application Laid-Open No. 2005-281013, adding Bi and Mn to (Li, Na, K)(Nb, Ta)O3-based piezoelectric/electrostrictive ceramic compositions is also proposed in order to improve the deliquescent properties and insulation properties of the (Li, Na, K)(Nb, Ta)O3-based piezoelectric/electrostrictive ceramic compositions.
However, conventional (Li, Na, K)(Nb, Ta)O3-based piezoelectric/electrostrictive ceramic compositions have the problem that they fail in offering sufficient electric field-induced distortion at the time of application of a high electric field, which is an important factor for piezoelectric/electrostrictive actuators.